When storing distinguishable objects, such as tape cartridges, within a defined area, in which various object removal and replacement opportunities exist, it is generally desirable to provide a mechanism for identifying those objects present within the defined area.
One approach to providing the desired object identification is to attach bar codes to each of the objects and to subsequently read these bar codes when an object presence/absence determination is sought. Since bar codes are generally read by a reader placed in substantial proximity to a bar code imprint or sticker, a mechanism for moving a bar code reader into a suitable reading position is generally needed. For example, in a tape library container, where individual tape cartridges are affixed with bar codes for later identification, a robot arm may be employed to move a bar code reader into position to read bar codes disposed on individual tape cartridges. While this approach may succeed in identifying the tape cartridges within a defined area, such as a tape cartridge container, equipment, such as the robot arm, and appropriate engineering, such as robot arm programming, will generally be needed in order to make such a system operational. Moreover, considerable time may be expended moving the robot arm to various reading locations in order to complete one full presence detection operation. Furthermore, the available locations in which objects may be stored in a container may be limited by the need to gain line-of-sight access to a bar code by a mobile bar code reader.
Another approach to providing object presence/absence detection is to equip objects, whose presence information is sought, with a computer chip able to intelligently communicate with an appropriately located controller or computer. This approach would generally provide each equipped object with the ability to intelligently transmit and receive a broad range of information over a connection to a central controller. While this approach would provide a central controller with the ability to perform object presence detection, this solution generally represents an unnecessarily elaborate, complicated, and expensive approach to a relatively simple communication function.